This invention relates to machine-readable optical discs of all types, including for example digital discs such as compact discs (CD""s), digital video discs (DVD""s), CDROM""s, and the like.
Conventional optical discs have reached widespread acceptance as a low-cost, reliable storage medium for digital information including music, video, and data. One of the traditional advantages of optical discs is their long life.
However, in some applications, the long life of the conventional optical disc may represent a disadvantage. For example, if music, movies or software is to be made available for a limited time period, the original optical disc must be returned at the end of the rental period.
A need presently exists for an improved machine-readable optical disc that eliminates the need for the return of an optical disc at the end of a rental period.
According to a first aspect of this invention, an optical disc comprising machine-readable, information-encoding features is provided with a barrier layer releasably coupled to the disc. This barrier layer is configured to prevent machine-reading of the disc. A reading-inhibit agent is included in the disc, and is activated by removal of the barrier layer. This reading-inhibit agent is operative, after it is activated, to alter the disc to inhibit reading of the disc. Both the barrier layer and the reading-inhibit agent can take many forms, as discussed by way of example below.
According to another aspect of this invention, an optical disc comprising machine-readable, information-encoding features is provided with a reading-inhibit agent that is activated by machine-reading the disc. This reading-inhibit agent is operative, after it is activated, to alter the disc to inhibit reading of the disc. In alternate embodiments, the reading-inhibit agent may be activated by optical radiation incident on the disc during machine-reading of the disc, or by rotation of the disc during machine-reading of the disc.
According to a third aspect of this invention, a method is provided for inhibiting reading of an optical disc. According to this method, an optical disc is provided comprising machine-readable, information-encoding features, and a reading-inhibit agent. The reading-inhibit agent is activated by optical radiation, and is operative, once activated, to alter the disc to inhibit reading. A reading device is provided to read the disc, and this reading device comprises a source of optical radiation. According to the method of this invention, the disc is read with the reading device, and the inhibit agent is concurrently activated with optical radiation from the source. The source of optical radiation that activates the reading-inhibit agent can either be the source of optical radiation that forms the reading beam, or a second source, separate from the reading beam source.